A study to evaluate the benefits and side effects of the combination of three drugs, leucovorin, 5FU, and Gemzar, used in chemotherapy for cancer patients. Patients who enter this study have cancer, which has progressed despite standard therapy, or for which there is no standard therapy. All blood work and physical examinations necessary for registration in the study will have been done no longer than seven days before starting. X-rays and scans must be done no more than five weeks before the initial treatment. Registration will take place one week before the start of the treatment. Based on assignment at the time of registration, patients will receive either leucovorin followed by 5FU, which is followed by Gemzar, or they will be randomly assigned to receive Gemzar, then leucovorin, then 5FU. All drugs will be given three times a week for four weeks. Disease assessment will follow the second cycle of therapy unless symptoms prompt earlier assessment. Patients with a complete or partial response or stable disease may be considered for further therapy. Patients continuing therapy will have disease assessment after every two cycles, or about every two months.